Process for preparing highly active double metal cyanide catalysts and their use in the synthesis of polyether polyols

ABSTRACT

The present invention relates to a process of preparing a double metal cyanide (DMC) complex catalyst with an improved catalytic activity useful for epoxide polymerization. It also relates to the DMC catalyst obtainable by said process, as well as to polyether polyols prepared by a polymerization reaction using said DMC catalyst.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national phase under the provisions of 35U.S.C. §371 of International Patent Application No. PCT/EP12/59081 filedMay 16, 2012, which in turn claims priority of European PatentApplication No. 11382156.5 filed May 17, 2011. The disclosures of suchinternational patent application and European priority patentapplication are hereby incorporated herein by reference in theirrespective entireties, for all purposes.

FIELD OF THE INVENTION

The present invention relates to a process for the preparation of doublemetal cyanide (DMC) complex catalysts with an improved catalyticactivity useful for epoxide polymerization, as well as to a process forpreparing polyether polyols using said catalysts. In particular, the DMCcatalysts of the invention are easy to prepare, have a very highactivity and provide polyol products having low unsaturations and lowpolidispersity.

BACKGROUND OF THE INVENTION

Double metal cyanide (DMC) complexes are well-known catalysts forepoxide polymerization. These catalysts are highly active and givepolyether polyols having low unsaturation, a very narrow molecularweight distribution and consequently, a low polydispersity.

DMC catalysts were discovered more than forty years ago by researchesfrom the General Tire and Rubber Company (U.S. Pat. Nos. 3,404,109;3,427,256; 3,427,334 and 3,941,849). Since then, the technology forproducing DMC catalysts has been improved by different companies.

Conventional process for the preparation of DMC catalysts directed tothe epoxide polymerization is well-disclosed in EP0090444, EP0090445,EP1022300, EP0555053, EP0700949, EP0894108 and EP0932445. This processinvolves the reaction of aqueous solutions of metal salts and metalcyanide salts to form a precipitate of the DMC compound. A low molecularweight organic complexing agent, typically an ether or an alcohol suchas tert-butyl alcohol, is included in the catalyst preparation. Theactivity of DMC catalysts has been greatly enhanced by incorporating, inaddition to the organic complexing agent, functionalized ligands such aspolyether polyols.

The resulting water-insoluble double metal cyanide complex catalystwhich precipitates from solution must thereafter be recovered from theaqueous reaction medium, washed to remove undesirable by products andimpurities, and dried in order to obtain the catalyst in a form suitablefor use in a polymerization process.

To this aim, the solid complex is firstly reslurried in a mixture of anorganic complexing agent, generally tert-butyl alcohol, and water andthereafter in pure organic complexing agent, being subsequently filteredand dried under vacuum at a moderate temperature.

Different modifications with respect to the order of addition ofreactants or the time to incorporate the organic complexing agent havebeen published. For example, EP0555053 describes the addition of theaqueous solution of the metal salt over the aqueous solution of themetal cyanide salt, whereas in EP0743093 the reverse order of additionis disclosed, showing the advantageous effect on the activity of theresulting DMC catalyst.

However, there are few documents describing the effect of the washingstep on the catalytic activity. EP0700949 shows that the washing step isnecessary in order to give an active catalyst and that multiple washingsteps could lead to the preparation of even more active catalysts. Saidstep is carried out by washing the precipitate with an aqueous solutionof tert-butyl alcohol (70%).

Some references mention that an excessive use of water in the washingstep should be avoided, since the excess of the non-reacting metal saltcould be removed giving rise to a lower-active catalyst. In addition, inorder to suit the drying of the catalyst, is desirable to wash it withthe organic complexing agent only or with a mixture of water and organiccomplexing agent (EP0555053). In EP0894108, the catalyst is washed withan aqueous solution containing the organic complexing agent and apolyether polyol in a range 40-70% and 0.1-8%, respectively.

The isolation of the dry, active double metal cyanide complex catalystis generally complicated and therefore, a convenient and effectivemethod of preparing said catalysts which can be readily isolated byconventional and straight-forward filtration techniques would be ofparticular interest.

On the other hand, it has been shown (EP0700949, EP0894108, EP0932445)that the incorporation of polyether polyols or functionalized polymersto the catalyst, in addition to the metal salt, the metal cyanide saltand the organic complexing agent, provides improved DMC catalysts withhigher activities and allows the production of polyether polyols withlow catalyst concentrations.

In EP0090444, the suspension of a DMC catalyst in a propoxilatedglycerol with molecular weight ranged from 200 to 400 is described. InEP0700949 it is shown that the use of polyether polyol ligands withmolecular weights higher than 500 provides DMC catalysts with animproved activity. EP0894108 discloses catalysts capable of polymerizingpropylene oxide at a rate in excess of 1 Kg PO/g Co/min at 100 ppmcatalyst, based on the weight of finished polyether, at 105° C., saidcatalyst having polyethers with a number average molecular weight lessthan 500, and no tertiary hydroxyl groups. However, all of the examplesof these documents describe the use of polyether polyols obtained bybasic catalysis and the state of the art is silent about the influenceof the acidic nature of the polyether polyol ligands.

DMC catalysts with improved properties are thus needed.

In spite of the different procedures to provide DMC catalysts havinggood activity for epoxide polymerization, catalyst with even improvedactivity are still desirable in order to reduce the catalyst level usedin said polymerization reactions.

Furthermore, since DMC catalysts generally require activation timeshigher than one hour which have a negatively impact on thepolymerization cycle times, it is also desirable to reduce saidactivation times.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a convenient and effective method ofpreparing double metal cyanide complex catalysts which can be rapidlyisolated by conventional and straight-forward techniques, with reducedactivation times and exceptional catalytic activity.

In this sense, the authors of the present invention have surprisinglyfound that carrying out a first washing step of the precipitated solidobtained after the synthesis of the DMC compound, in an aqueoussolution, without any organic complexing agent, leads to the formationof a DMC catalyst with a remarkable higher catalytic activity, whichfurther requires substantially lower activation times.

In addition, the use of a polyether polyol obtained by acidic catalysis,as a ligand of the DMC catalyst, allows a further improvement on theactivity of the catalyst in the process for the preparation of polyetherpolyols.

Therefore, a first aspect of the present invention refers to a process(from now onwards process 1) of preparing a double metal cyanide (DMC)complex catalyst, said process comprising:

-   -   a) synthesizing a solid double metal cyanide catalyst in the        presence of an organic complexing agent and a polyether polyol        ligand;    -   b) first washing the catalyst obtained in step a) with an        aqueous solution comprising:        -   90-100% by weight of water; and        -   0-10% by weight of a polyether polyol ligand,    -    to form a slurry, wherein the aqueous solution does not contain        any organic complexing agent.

Preferably, the process further comprises:

-   -   c) isolating the catalyst from the slurry obtained in step b);        and    -   d) washing the solid catalyst obtained in step c) with a        solution comprising:        -   90-100% by weight of an organic complexing agent, and        -   0-10% by weight of a polyether polyol ligand.

Surprisingly, a synergistic effect on the activity of the catalyst hasbeen found when combining the use of the particular aqueous solution inthe above mentioned washing step (step b) of the process 1 of theinvention) with:

-   -   the use of an excess amount of an organic complexing agent in a        subsequent washing step (step d) of the process 1 of the        invention)    -   and/or    -   the use of an excess amount of an organic complexing agent in        the synthesis of the DMC catalyst (step a) of the process 1 of        the invention).

In a second aspect, the invention refers to a DMC catalyst obtainable bythe process 1 as defined above.

Additionally, a third aspect of the invention refers to a DMC catalystas defined above which comprises:

-   -   at least one double metal cyanide;    -   at least one organic complexing agent; and    -   at least one polyether polyol ligand having a molecular weight        lower than 2000, which has been obtained by acidic catalysis.

The fourth aspect of the present invention relates to a process (fromnow onwards process 2) for polymerizing an epoxide, said processcomprising the reaction of an epoxide with an initiator in the presenceof a DMC catalyst as defined above.

A further synergistic effect on the activity of the DMC catalyst in thepolymerization of epoxides can be obtained when the catalyst contains,as a ligand, a polyether polyol synthesized by acidic catalysis, and thesame polyether polyol is used as initiator of the polymerizationreaction.

Finally, the invention also refers to a polyether polyol obtainable bythe process 2 as defined above.

DETAILED DESCRIPTION OF THE INVENTION

The process 1 of the invention provides a DMC catalyst with a remarkablehigher catalytic activity useful for epoxide polymerization, whichfurther requires substantially lower activation times as pointed out inexample 8 (table I). Due to its improved activity, it can be used atvery low concentrations, such as 30 ppm or less. At such low catalystlevels, the catalyst can often be left in the polymer product without anadverse impact on the product quality thus, effectively avoiding theneed for a catalyst removal step. However, if a polymer product with avery high purity is required, the catalyst can be readily removed byfiltration, for example following the procedure described inEP1338618B1. According to a preferred embodiment, the catalyst isremoved to concentrations below 10 ppm or below 5 ppm.

Furthermore, the DMC catalyst obtained following the process 1 of theinvention provides polyether polyols with lower unsaturation levels andlower polidipersity as shown in example 8 (table III).

Accordingly, the invention provides a process (process 1) for preparingDMC catalysts with higher activities useful for epoxide polymerization.

In a first step, the process comprises the synthesis of a solid doublemetal cyanide catalyst. This step is generally performed by reacting, inan aqueous solution, a water-soluble metal salt (in excess) and awater-soluble metal cyanide salt in the presence of a polyether polyolligand and an organic complexing agent.

In a preferred embodiment of the process of the invention, aqueoussolutions of a water-soluble metal salt and a water-soluble metalcyanide salt are first reacted in the presence of the organic complexingagent using efficient mixing to produce a catalyst slurry. The metalsalt is used in excess. The catalyst slurry contains the reactionproduct of the metal salt and the metal cyanide salt, which is a doublemetal cyanide compound. Also present are excess metal salt, water, andorganic complexing agent, each is incorporated to some extent in thecatalyst structure. In another preferred embodiment, the mixture of theaqueous solution containing the water-soluble metal salt and the aqueoussolution containing the water-soluble metal cyanide salt takes place ata temperature ranging from 30 to 70° C., more preferably from 40 to 60°C., even more preferably at about 50° C.

The water-soluble metal salt preferably has the general formula MA_(n)wherein:

-   -   M is a cation selected form the group consisting of Zn(II),        Fe(II), Ni(II), Mn(II), Co(II), Sn(II), Pb(II), Fe(III), Mo(IV),        Mo(VI), Al(III), V(V), V(IV), Sr(II), W(IV), W(VI), Cu(II) and        Cr(III). Preferably, M is a cation selected from Zn(II), Fe(II),        Ni(II), Mn(II) and Co(II);    -   A is an anion selected from the group consisting of halide,        hydroxide, sulfate, carbonate, vanadate, cyanide, oxalate,        thiocyanate, isocyanate, isothiocyanate, carboxylate and        nitrate. Preferably, A is a cation selected from halide;    -   n is 1, 2 or 3 and satisfies the valency state of M.

Examples of suitable metal salts include, but are not limited to, zincchloride, zinc bromide, zinc acetate, zinc acetonylacetonate, zincbenzoate, zinc nitrate, iron(II) sulfate, iron(II) bromide, cobalt(II)chloride, cobalt(II) thiocyanate, nickel(II) formate, nickel(II) nitrateand the like and mixtures thereof.

The water-soluble metal cyanide salts preferably have the formulaD_(x)[E_(y)(CN)₆], wherein:

-   -   D is an alkali metal ion or alkaline earth metal ion;    -   E is a cation selected from the group consisting of Co(II),        Co(III), Fe(II), Fe(III), Mn(II), Mn(III), Cr(II), Cr(III),        Ni(II), Ir(III), Rh(III), Ru(II), V(IV) and V(V). Preferably, E        is selected from Co(II), Fe(II), Ni(II), Co(III) and Fe(III);    -   x and y are integers greater than or equal to 1, the sum of the        charges of x and y balances the charge of the cyanide (CN)        group.

Suitable water-soluble metal cyanide salts include, but are not limitedto, potassium hexacyanocobaltate (III), potassium hexacyanoferrate (II),potassium hexacyanoferrate (III), calcium hexacyanocobaltate (III),lithium hexacyanocobaltate (III), and the like.

The organic complexing agent can be included with either or both of theaqueous salt solutions, or it can be added to the catalyst slurryimmediately following precipitation of the DMC compound. It is generallypreferred to pre-mix the organic complexing agent with either aqueoussolution before combining the reactants. Usually, an excess amount ofthe complexing agent is used.

Generally, the complexing agent must be relatively soluble in water.Suitable organic complexing agents are those commonly known in the art,for example in U.S. Pat. No. 5,158,922. Preferred organic complexingagents are water-soluble heteroatom-containing organic compounds thatcan complex with the double metal cyanide compound. More preferably, theorganic complexing agents are water-soluble heteroatom-containingcompounds selected from monoalcohols, aldehydes, ketones, ethers,esters, amides, ureas, nitriles, sulfides and mixtures thereof.Preferred organic complexing agents are water-soluble aliphatic alcoholsselected from the group consisting of ethanol, isopropyl alcohol,n-butyl alcohol, iso-butyl alcohol, sec-butyl alcohol and tert-butylalcohol. Tert-butyl alcohol (TBA) is particularly preferred.

The aqueous metal salt and metal cyanide salt solutions (or their DMCreaction product) need to be mixed efficiently with the organiccomplexing agent to produce the most active form of the catalyst. Astirrer can be conveniently used to achieve efficient mixing.

Examples of double metal cyanide compounds resulting from this reactioninclude, for example, zinc hexacyanocobaltate (III), zinchexacyanoferrate (III), nickel hexacyanoferrate (II), cobalthexacyanocobaltate (III) and the like. Zinc hexacyanocobaltate (III) ispreferred.

The catalyst slurry produced after the mixing of the aqueous solutionsin the presence of the organic complexing agent is then combined with apolyether polyol ligand. This step is preferably performed using astirrer so that an efficient mixture of the catalyst slurry and thepolyether polyol takes place.

This mixture is preferably performed at a temperature ranging from 30 to70° C., more preferably from 40 to 60° C., even more preferably at about50° C.

Suitable polyethers include those produced by ring-openingpolymerization of cyclic ethers, and include epoxide polymers, oxetanepolymers, tetrahydrofuran polymers and the like. Any method of catalysiscan be used to make the polyethers. The polyethers can have any desiredend groups, including, for example, hydroxyl, amine, ester, ether or thelike. Preferred polyethers are polyether polyols having average hydroxylfunctionalities from about 2 to about 8. Also preferred are polyetherpolyols having a number average molecular weight lower than 2000, morepreferably between 200 and 1000, even more preferably between 300 and800. These are usually made by polymerizing epoxides in the presence ofactive hydrogen-containing initiators and basic, acidic ororganometallic catalysts (including DMC catalysts).

Useful polyether polyols include poly(oxypropylene)polyols, ethyleneoxide-capped poly(oxypropylene)polyols, mixed ethylene oxide-propyleneoxide polyols, butylenes oxide polymers, butylenes oxide copolymers withethylene oxide and/or propylene oxide, polytetra methylene ether glycolsand the like. Most preferred are poly(oxypropylene)polyols, particularlydiols and triols having number average molecular weights lower than2000, more preferably between 200 and 1000, even more preferably between300 and 800.

More preferably, the polyether polyol used in the process 1 of theinvention has been synthesized by acidic catalysis, i.e. by polymerizingan epoxide in the presence of active hydrogen-containing initiator andacidic catalysts. Examples of suitable acidic catalysts include Lewisacids such as BF₃, SbF₅, Y(CF₃SO₃)₃, or Brönstedt acids such as CF₃SO₃H,HBF₄, HPF₆, HSbF₆.

Using a polyether obtained by acidic catalysis in the process 1 of thepresent invention, in addition to the organic complexing agent,surprisingly enhances the catalyst activity compared with the activityof a similar catalyst prepared in the presence of a polyether obtainedby basic or organometallic catalysis.

Once the polyether has been combined with the double metal cyanidecompound, a polyether-containing solid catalyst is isolated from thecatalyst slurry. This is accomplished by any convenient means, such asfiltration, centrifugation or the like.

In a particular embodiment, enough reactants are used to give a solidDMC catalyst that contains:

-   -   30-80% by weight of the double metal cyanide compound;    -   1-10% by weight of water;    -   1-30% by weight of the organic complexing agent; and    -   1-30% by weight of the polyether polyol ligand.

Preferably, the total amount of the organic complexing agent and thepolyether polyol is from 5% to 60% by weight with respect to the totalweight of the catalyst, more preferably from 10% to 50% by weight, evenmore preferably from 15% to 40% by weight.

The isolated polyether-containing solid catalyst is then first washedwith an aqueous solution comprising 90-100% by weight of water and 0-10%by weight of a polyether polyol. This aqueous solution is absent of anyorganic complexing agent as those mentioned above. The washing step isused to remove impurities from the catalyst that will render a lessactive catalyst if they are not removed.

It should be pointed out that no other washing step can be performedbefore this first washing step mentioned above once the isolatedpolyether-containing solid catalyst has been obtained in step a) of theprocess 1 of the invention.

It has been surprisingly found that the particular composition of theaqueous solution used in this washing step leads to a double metalcyanide catalyst with an enhanced activity. As shown in the examples ofthe present invention, this activity is higher when compared to thatobtained for a catalyst having been obtained using a process thatincludes a washing step using an aqueous solution comprising an organiccomplexing agent and a polyether polyol.

Preferably, the amount of polyether polyol ligand in the aqueoussolution in step b) is lower than 5% with respect to the total weight ofsolution. According to a further particular embodiment the amount ofpolyether polyol ligand in the aqueous solution in step b) is lower than4% with respect to the total weight of solution, preferably lower 3%.According to a further embodiment, the amount of polyether polyol ligandin the aqueous solution in step b) is between 0.1% and 2% with respectto the total weight of solution, preferably between 0.3% and 1.8%. In afurther particular embodiment, the amount of polyether polyol ligand inthe aqueous solution in step b) is 0%. The use of water in this washingstep without any content of polyether polyol ligand presumably leads toa double metal cyanide catalyst with an even higher activity.

The washing step is generally accomplished by reslurrying the catalystin the aqueous solution followed by a catalyst isolation step using anyconvenient means, such as filtration.

It has also been surprisingly found that the use of this particularaqueous solution in the washing step b) in combination with an excessamount of the organic complexing agent in the step a) and/or d),provides a synergistic effect on the activity of the DMC catalyst asshown in example 8 of the present invention.

Furthermore, the use of the particular aqueous solution in the washingstep also allows reducing the filtration times, which involves asignificant reduction of costs in an industrial scale process.Experimental tests at industrial scale have shown that filtration iscompleted in less than 3 hours in comparison to the at least 12 hoursrequired in other processes of the state of the art.

Although a single washing step suffices to give a catalyst with enhancedactivity, it is preferred to wash the catalyst more than once. In apreferred embodiment of the process 1 of the invention, the subsequentwash is non-aqueous and includes the reslurry of the double metalcyanide catalyst in an organic complexing agent or in a mixture of theorganic complexing agent and the polyether polyol used in the previouswashing step. More preferably, the double metal cyanide catalyst iswashed with a solution comprising 90-100% by weight of the organiccomplexing agent and 0-10% by weight of the polyether polyol. Theorganic complexing agent is preferably tert-butyl alcohol.

After the catalyst has been washed, it is usually preferred to dry itunder vacuum until the catalyst reaches a constant weight. The catalystcan be dried at temperatures within the range of about 50° C. to 120°C., more preferably from 60° C. to 110° C., even more preferably from90° C. to 110° C. Contrary to the state of the art (see for exampleEP0555053) wherein temperatures ranging from 15° C. to 40° C. arerequired in order not to deactivate the catalyst, the process 1 of theinvention allows an effective drying step at higher temperatures withoutaffecting the structure of the catalyst, and thus requiring less time.

The dry catalyst can be crushed to yield a highly active catalyst inpowder form appropriate for use in a ring-opening polymerizationreaction.

The process 1 of the invention provides double metal cyanide complexcatalysts with reduced activation times and exceptional catalyticactivity. In particular, the first washing step of the precipitatedsolid obtained after the synthesis of the DMC catalyst, in an aqueoussolution, without any organic complexing agent, leads to the formationof a DMC catalyst with a remarkable higher catalytic activity than thatfor DMC catalysts subjected to a first washing step using a solutioncontaining organic complexing agents.

This washing step, combined with the use in the reaction process leadingto the double metal cyanide catalyst of a polyether polyol, obtained byacidic catalysis, allows obtaining a higher improvement on the activityof the catalyst in the process for the preparation of polyether polyols.

In view of the improved activity of this catalyst when compared to otherDMC catalyst obtained following conventional methods, the process 1defined above would necessarily leads to the preparation of a catalystwith a particular structure that confers this enhanced activity.

Therefore, in a second aspect the invention also refers to a doublemetal cyanide catalyst obtainable by the process 1 as define above.

In a particular embodiment, the catalyst obtainable by the process ofclaim 1 is also characterized by comprising:

-   -   at least one double metal cyanide compound;    -   at least one organic complexing agent; and    -   at least one polyether polyol ligand having a molecular weight        lower than 2000.

Preferably the double metal cyanide compound is selected from zinchexacyanocobaltate (III), zinc hexacyanoferrate (III), nickelhexacyanoferrate (II), cobalt hexacyanocobaltate (III) and the like.Zinc hexacyanocobaltate (III) is preferred.

Also preferably, organic complexing agents are water-solubleheteroatom-containing organic compounds that can complex with the doublemetal cyanide compound. Preferred organic complexing agents arewater-soluble aliphatic alcohols selected from the group consisting ofethanol, isopropyl alcohol, n-butyl alcohol, iso-butyl alcohol,sec-butyl alcohol and tert-butyl alcohol. Tert-butyl alcohol (TBA) isparticularly preferred.

Polyether polyol ligands include generally those produced byring-opening polymerization of cyclic ethers, and include epoxidepolymers, oxetane polymers, tetrahydrofuran polymers and the like.Preferred polyethers are polyether polyols having a number averagemolecular weight between 200 and 1000, more preferably between 300 and800.

Most preferred are poly(oxypropylene)polyols, particularly diols andtriols having number average molecular weights between 200 and 1000,more preferably between 300 and 800.

More preferably, the polyether polyol has been synthesized by acidiccatalysis, i.e. by polymerizing an epoxide in the presence of activehydrogen-containing initiator and acidic catalysts. Examples of suitableacidic catalysts include Lewis acids such as BF₃, SbF₅, Y(CF₃SO₃)₃, orBrönstedt acids such as CF₃SO₃H, HBF₄, HPF₆, HSbF₆.

In a particular embodiment, the double metal cyanide catalyst obtainableby process 1 of the invention comprises:

-   -   30-80% by weight of the double metal cyanide compound;    -   1-10% by weight of water;    -   1-30% by weight of the organic complexing agent; and    -   1-30% by weight of the polyether polyol ligand.

Preferably, the total amount of the organic complexing agent and thepolyether polyol is from 5% to 60% by weight with respect to the totalweight of the catalyst, more preferably from 10% to 50% by weight, evenmore preferably from 15% to 40% by weight.

It has been surprisingly found that DMC catalysts with a polyetherpolyol ligand obtained by acidic catalysis in their composition, whichhave been obtained according to the process 1 of the invention using theparticular washing composition, have a catalytic activity markedlyhigher than DMC catalysts of the state of the art, as well as a reducedactivation time.

The catalyst of the invention may be used in any of the polymerizationreactions known in the art wherein double metal cyanide complexcatalysts have been employed. More particularly, the catalyst is used ina process for making an epoxide polymer.

Therefore, the invention refers to a process (process 2) forpolymerizing an epoxide, said process comprising the reaction of anepoxide with an initiator in the presence of a DMC catalyst as definedabove.

Preferred epoxides are ethylene oxide, propylene oxide, butane oxide,styrene oxide and the like, and mixtures thereof. The process can beused to make random or block copolymers. The epoxide polymer can be, forexample, a polyether polyol derived from the polymerization of anepoxide in the presence of a hydroxyl group-containing initiator.

Other monomers that will copolymerize with an epoxide in the presence ofthe DMC catalyst can be included in the process 2 of the invention tomake other types of epoxide polymers. Any of the copolymers known in theart made using conventional DMC catalysts can be made with the catalystsof the invention. For example, epoxides copolymerize with oxetanes togive polyethers, or with anhydrides to give polyester or polyetheresterpolyols.

Preferably, the polyether polyol used as a ligand of the DMC catalyst isa polyether polyol having been synthesized by acidic catalysis. Alsopreferably, the initiator of the polymerization reaction has beenobtained by acidic catalysis, being more preferably the use of apolyether polyol such as the one used as a ligand of the catalyst.

The acidic nature of the ligand and the initiator improves the catalyticactivity of the DMC catalyst since a further synergistic effect in theactivity of the catalyst has been observed in epoxide polymerizationreactions when an acidic polyether polyol is used as a ligand of thecatalyst and as initiator of the polymerization reaction.

In a preferred embodiment of the invention, the polymerization reactionin the presence of the catalyst of the invention takes place at atemperature higher than 110° C., more preferably from 120° C. to 160° C.

The use of the DMC catalyst of the invention in the epoxidepolymerization reaction allows the preparation of polyether polyols withlower unsaturation and lower polydispersity as pointed out in example 8(table III). This is particularly advantageous since a lowpolydispersity provides polyether polyols with a lower viscosity, aproperty which is highly desirable for the subsequent applications ofthis type of polymers. Therefore, this polymerization process (process2) leads to the preparation of polyether polyols with improvedproperties.

Consequently, the invention also refers to a polyether polyol obtainableby the process 2 as defined above.

The following examples merely illustrate the invention. Those skilled inthe art will recognize many variations that are within the spirit of theinvention and scope of the claims.

EXAMPLES

General Remarks

In the following examples, the terms “A” and “B” following the type ofpolyol means that the polyol has been synthesized by acidic catalysisand basic catalysis, respectively.

Example 1 Preparation of Zinc Hexacyanocobaltate Catalyst Using TBA asOrganic Complexing Agent and Polypropylene Glycol (PPG) B (MWn 400) asPolyol

1^(st) Step

Potassium hexacyanocobaltate (7.5 g) is dissolved in deionized water(100 ml) in a beaker (Solution A). Zinc chloride (75 g) and tert-butylalcohol TBA (50 mL) are dissolved in deonized water (275 mL) in a secondbeaker (Solution B).

Solution B is heated at a temperature of 50° C. Subsequently, solution Ais slowly added for 30 minutes to the solution B while stirring at 400rpm. The aqueous zinc chloride and TBA solution and the cobalt saltsolution are combined using a stirrer to intimately and efficiently mixboth aqueous solutions. The mixture is held post-reacting for 30 minutesat the same temperature to form a slurry of zinc hexacyanocobaltate.

A third solution (solution C) is prepared by dissolving a 400 mol. wtdiol (8 g, polypropylene glycol (PPG)) in deonized water (50 mL) and TBA(2 mL). Said diol has been synthesized by basic catalysis followingprocedures widely known in the art.

Solution C (the PPG/water/TBA mixture) is added to the aqueous slurryzinc hexacyanocobaltate for 5 minutes, and the product is stirred for 10additional minutes. The mixture is filtered under pressure to isolatethe solid.

2^(nd) Step

The solid cake is reslurried in water (150 mL) for 30 minutes at atemperature of 50° C. and subsequently, additional 400 mol. wt diol PPG(2 g) is added. The mixture is homogenized by stirring for 10 minutesand filtered.

3^(rd) Step

The solid cake obtained after the second step is reslurried in TBA (185mL) for 30 minutes at a temperature of 50° C. and subsequently,additional 400 mol. wt diol PPG (1 g) is added. The mixture ishomogenized by stirring for 5 minutes and filtered.

The resulting solid catalyst (catalyst 1) is dried under vacuum at 100°C. and 10 mbar to constant weight.

Example 2 Preparation of Zinc Hexacyanocobaltate Catalyst Using TBA asOrganic Complexing Agent at a 50% Higher Proportion than in Example 1,and Polypropylene Glycol (PPG) B (MWn 400) as Polyol

1^(st) Step

Potassium hexacyanocobaltate (7.5 g) is dissolved in deionized water(100 ml) in a beaker (Solution A). Zinc chloride (75 g) and tert-butylalcohol TBA (75 mL) are dissolved in deonized water (275 mL) in a secondbeaker (Solution B).

Solution B is heated at a temperature of 50° C. Subsequently, solution Ais slowly added for 30 minutes to the solution B while stirring at 400rpm. The aqueous zinc chloride and TBA solution and the cobalt saltsolution are combined using a stirrer to intimately and efficiently mixboth aqueous solutions. The mixture is held post-reacting for 30 minutesat the same temperature to form a slurry of zinc hexacyanocobaltate.

A third solution (solution C) is prepared by dissolving a 400 mol. wtdiol (8 g, polypropylene glycol (PPG)) in deonized water (50 mL) and TBA(3 mL). Said diol has been synthesized by basic catalysis followingprocedures widely known in the art.

Solution C (the PPG/water/TBA mixture) is added to the aqueous slurryzinc hexacyanocobaltate for 5 minutes, and the product is stirred for 10additional minutes. The mixture is filtered under pressure to isolatethe solid.

2^(nd) Step

The solid cake is reslurried in water (208 mL) for 30 minutes at atemperature of 50° C. and subsequently, additional 400 mol. wt diol PPG(2 g) is added. The mixture is homogenized by stirring for 10 minutesand filtered.

3^(rd) Step

The solid cake obtained after the second step is reslurried in TBA (280mL) for 30 minutes at a temperature of 50° C. and subsequently,additional 400 mol. wt diol PPG (1 g) is added. The mixture ishomogenized by stirring for 5 minutes and filtered.

The resulting solid catalyst (catalyst 2) is dried under vacuum at 100°C. and 10 mbar to constant weight.

Example 3 Preparation of Zinc Hexacyanocobaltate Catalyst Using TBA asOrganic Complexing Agent (at a 50% Higher Proportion than in Example 1,or as Example 2) and Propoxylated Glycerol A (MWn 700) as Polyol

1^(st) Step

Potassium hexacyanocobaltate (7.5 g) is dissolved in deionized water(100 ml) in a beaker (Solution A). Zinc chloride (75 g) and tert-butylalcohol TBA (75 mL) are dissolved in deonized water (275 mL) in a secondbeaker (Solution B).

Solution B is heated at a temperature of 50° C. Subsequently, solution Ais slowly added for 30 minutes to the solution B while stirring at 400rpm. The aqueous zinc chloride and TBA solution and the cobalt saltsolution are combined using a stirrer to intimately and effectively mixboth aqueous solutions. The mixture is held post-reacting for 30 minutesat the same temperature to form a slurry of zinc hexacyanocobaltate.

A third solution (solution C) is prepared by dissolving a 700 mol. wt.triol (14 g, a propoxylated glycerol) in deonized water (50 mL) and TBA(3 mL). Said triol has been synthesized by acidic catalysis followingprocedures widely known in the art.

Solution C (the propoxylated glycerol/water/TBA mixture) is added to theaqueous slurry zinc hexacyanocobaltate for 5 minutes, and the product isstirred for 10 additional minutes. The mixture is filtered underpressure to isolate the solid.

2^(nd) Step

The solid cake is reslurried in water (208 mL) for 30 minutes at atemperature of 50° C. and subsequently, additional 700 mol. wt triol(propoxylated glycerol) (3.5 g) is added. The mixture is homogenized bystirring for 10 minutes and filtered.

3^(rd) Step

The solid cake obtained after the second step is reslurried in TBA (280mL) for 30 minutes at a temperature of 50° C. and subsequently,additional 700 mol. wt triol (propoxylated glycerol) (1.75 g) is added.The mixture is homogenized by stirring for 5 minutes and filtered.

The resulting solid catalyst (catalyst 3) is dried under vacuum at 100°C. and 10 mbar to constant weight.

Comparative Example 4 Preparation of Zinc Hexacyanocobaltate CatalystUsing TBA as Organic Complexing Agent and Polypropylene Glycol (PPG) B(MW 400) as Polyol. Second Step 70% TBA/H₂O

1^(st) Step

Potassium hexacyanocobaltate (7.5 g) is dissolved in deionized water(100 ml) in a beaker (Solution A). Zinc chloride (75 g) and tert-butylalcohol TBA (50 mL) are dissolved in deonized water (275 mL) in a secondbeaker (Solution B).

Solution B is heated at a temperature of 50° C. Subsequently, solution Ais slowly added for 30 minutes to the solution B while stirring at 400rpm. The aqueous zinc chloride and TBA solution and the cobalt saltsolution are combined using a stirrer to intimately and efficiently mixboth aqueous solutions. The mixture is held post-reacting for 30 minutesat the same temperature to form a slurry of zinc hexacyanocobaltate.

A third solution (solution C) is prepared by dissolving a 400 mol. wt.diol (8 g, polypropylene glycol (PPG)) in deonized water (50 mL) and TBA(2 mL). Said diol has been synthesized by basic catalysis followingprocedures widely known in the art.

Solution C (the PPG/water/TBA mixture) is added to the aqueous slurryzinc hexacyanocobaltate for 5 minutes, and the product is stirred for 10additional minutes. The mixture is filtered under pressure to isolatethe solid.

2^(nd) Step

The solid cake is reslurried in an aqueous solution (185 mL) containingTBA (70%) for 30 minutes at a temperature of 50° C. and subsequently,additional 400 mol. wt diol PPG (2 g) is added. The mixture ishomogenized by stirring for 10 minutes and filtered.

3^(rd) Step

The solid cake obtained after the second step is reslurried in TBA (185mL) for 30 minutes at a temperature of 50° C. and subsequently,additional 400 mol. wt diol PPG (1 g) is added. The mixture ishomogenized by stirring for 5 minutes and filtered.

The resulting solid catalyst (comparative catalyst 4) is dried undervacuum at 100° C. and 10 mbar to constant weight.

Comparative Example 5 Preparation of Zinc Hexacyanocobaltate CatalystUsing TBA as Organic Complexing Agent and Polypropylene Glycol (PPG) B(MW 400) as Polyol. Second Step 50% TBA/H₂O

1^(st) Step

Potassium hexacyanocobaltate (7.5 g) is dissolved in deionized water(100 ml) in a beaker (Solution A). Zinc chloride (75 g) and tert-butylalcohol TBA (50 mL) are dissolved in deonized water (275 mL) in a secondbeaker (Solution B).

Solution B is heated at a temperature of 50° C. Subsequently, solution Ais slowly added for 30 minutes to the solution B while stirring at 400rpm. The aqueous zinc chloride and TBA solution and the cobalt saltsolution are combined using a stirrer to intimately and efficiently mixboth aqueous solutions. The mixture is held post-reacting for 30 minutesat the same temperature to form a slurry of zinc hexacyanocobaltate.

A third solution (solution C) is prepared by dissolving a 400 mol. wt.diol (8 g, polypropylene glycol (PPG)) in deonized water (50 mL) and TBA(2 mL). Said diol has been synthesized by basic catalysis followingprocedures widely known in the art.

Solution C (the PPG/water/TBA mixture) is added to the aqueous slurryzinc hexacyanocobaltate for 5 minutes, and the product is stirred for 10additional minutes. The mixture is filtered under pressure to isolatethe solid.

2^(nd) Step

The solid cake is reslurried in an aqueous solution (185 mL) containingTBA (50%) for 30 minutes at a temperature of 50° C. and subsequently,additional 400 mol. wt diol PPG (2 g) is added. The mixture ishomogenized by stirring for 10 minutes and filtered.

3^(rd) Step

The solid cake obtained after the second step is reslurried in TBA (185mL) for 30 minutes at a temperature of 50° C. and subsequently,additional 400 mol. wt diol PPG (1 g) is added. The mixture ishomogenized by stirring for 5 minutes and filtered.

The resulting solid catalyst (comparative catalyst 5) is dried undervacuum at 100° C. and 10 mbar to constant weight.

Comparative Example 6 Preparation of Zinc Hexacyanocobaltate CatalystUsing TBA as Organic Complexing Agent and Polypropylene Glycol (PPG) B(MW 400) as Polyol. Second Step 100% TBA

1^(st) Step

Potassium hexacyanocobaltate (7.5 g) is dissolved in deionized water(100 ml) in a beaker (Solution A). Zinc chloride (75 g) and tert-butylalcohol TBA (50 mL) are dissolved in deonized water (275 mL) in a secondbeaker (Solution B).

Solution B is heated at a temperature of 50° C. Subsequently, solution Ais slowly added for 30 minutes to the solution B while stirring at 400rpm. The aqueous zinc chloride and TBA solution and the cobalt saltsolution are combined using a stirrer to intimately and efficiently mixboth aqueous solutions. The mixture is held post-reacting for 30 minutesat the same temperature to form a slurry of zinc hexacyanocobaltate.

A third solution (solution C) is prepared by dissolving a 400 mol. wt.diol (8 g, polypropylene glycol (PPG)) in deonized water (50 mL) and TBA(2 mL). Said diol has been synthesized by basic catalysis followingprocedures widely known in the art.

Solution C (the PPG/water/TBA mixture) is added to the aqueous slurryzinc hexacyanocobaltate for 5 minutes, and the product is stirred for 10additional minutes. The mixture is filtered under pressure to isolatethe solid.

2^(nd) Step

The solid cake is reslurried in TBA (185 mL) for 30 minutes at atemperature of 50° C. and subsequently, additional 400 mol. wt diol PPG(2 g) is added. The mixture is homogenized by stirring for 10 minutesand filtered.

3^(rd) Step

The solid cake obtained after the second step is reslurried in TBA (185mL) for 30 minutes at a temperature of 50° C. and subsequently,additional 400 mol. wt diol PPG (1 g) is added. The mixture ishomogenized by stirring for 5 minutes and filtered.

The resulting solid catalyst (comparative catalyst 6) is dried undervacuum at 100° C. and 10 mbar to constant weight.

Comparative Example 7 Preparation of Zinc Hexacyanocobaltate CatalystUsing TBA as Organic Complexing Agent at 50% Higher Proportion than inExample 4, and Polypropylene Glycol (PPG) B (MW 400) as Polyol. SecondStep 78% TBA/H₂O

1^(st) Step

Potassium hexacyanocobaltate (7.5 g) is dissolved in deionized water(100 ml) in a beaker (Solution A). Zinc chloride (75 g) and tert-butylalcohol TBA (75 mL) are dissolved in deonized water (275 mL) in a secondbeaker (Solution B).

Solution B is heated at a temperature of 50° C. Subsequently, solution Ais slowly added for 30 minutes to the solution B while stirring at 400rpm. The aqueous zinc chloride and TBA solution and the cobalt saltsolution are combined using a stirrer to intimately and efficiently mixboth aqueous solutions. The mixture is held post-reacting for 30 minutesat the same temperature to form a slurry of zinc hexacyanocobaltate.

A third solution (solution C) is prepared by dissolving a 400 mol. wt.diol (8 g, polypropylene glycol (PPG)) in deonized water (50 mL) and TBA(3 mL). Said diol has been synthesized by basic catalysis followingprocedures widely known in the art.

Solution C (the PPG/water/TBA mixture) is added to the aqueous slurryzinc hexacyanocobaltate for 5 minutes, and the product is stirred for 10additional minutes. The mixture is filtered under pressure to isolatethe solid.

2^(nd) Step

The solid cake is reslurried in a solution containing 195 mL of TBA and55 mL of water for 30 minutes at a temperature of 50° C. andsubsequently, additional 400 mol. wt diol PPG (2 g) is added. Themixture is homogenized by stirring for 10 minutes and filtered.

3^(rd) Step

The solid cake obtained after the second step is reslurried in TBA (280mL) for 30 minutes at a temperature of 50° C. and subsequently,additional 400 mol. wt diol PPG (1 g) is added. The mixture ishomogenized by stirring for 5 minutes and filtered.

The resulting solid catalyst (comparative catalyst 7) is dried undervacuum at 100° C. and 10 mbar to constant weight.

Example 8 Measurement of Catalyst Activity in the Synthesis of PolyolsUsing an Acidic Initiator

The catalysts prepared following examples 1-3 and comparative examples4-7 were tested in the copolymerization reaction of propylene oxide (PO)and ethylene oxide (EO).

The procedure was the following:

A two-liter Büchi reactor was charged with 200 g of a 700 mol. wt.polyether polyol triol (polymerization initiator) previously synthesizedby acidic catalysis. The compound was stirred at 1000 rpm and heated ata temperature of 140° C. under inert atmosphere. In order to remove thehumidity from the polyether polyol, vacuum was applied sparging with N₂during the required time to reach a humidity lower than 100 ppm.Subsequently, DMC catalyst (30 ppm) was added while stirring undervacuum for 10 minutes without sparging N₂.

Propylene oxide (30 g) was added to the reactor for the catalystactivation. An accelerated drop in reactor pressure soon occurred,indicating that the catalyst had become activated.

After initiation of the catalyst was verified, a mixture of propyleneoxide/ethylene oxide was slowly added to the reactor until the desiredmolecular weight was reached. The addition of propylene oxide wascarried out at 140° C. maintaining the reactor pressure below 1.5kg/cm².

Catalyst activity is measured from the slope of a PO/EO conversion vs.time plot.

Once the mixture of propylene oxide/ethylene oxide was completely added,the reaction mixture was held post-reacting for one hour in order tocomplete the conversion of monomers. Finally, residual monomers wereremoved under vacuum sparging with N₂ for one additional hour. Theresulting polymer is a poly(oxyethylene propylene)triol having averagenumber molecular weight 3500.

Table I shows the activity of the catalysts 1-3 and comparativecatalysts 4-6 and their activation times.

TABLE I Activity of the catalysts 1-3 and comparative catalysts 4-6measured following the process as described above. ActivationImprovement percentage time Catalyst activity with respect to (min)(g/min) comparative catalyst 4 Catalyst 1 22 18.2 21% Catalyst 2 21 31107% Catalyst 3 9 35.7 138% Comparative 32 15 Catalyst 4 Comparative 3311.6 −23% Catalyst 5 Comparative 30 12 −20% Catalyst 6

As shown in table I, the catalysts obtained following the process of theinvention (catalysts 1-3) are markedly more active than conventionalcatalyst of the state of the art and also show lower activation times.

In particular, the use of an aqueous solution lacking of organiccomplexing agent for washing the catalyst in the second step (example 1,catalyst 1) confers the catalyst with a 21% activity improvement withrespect to a catalyst obtained by conventional processes of the art(example 4, comparative catalyst 4) which use a washing aqueous solutioncontaining TBA. Second step using mixtures of TBA/H₂O lead to lessactive catalyst.

Furthermore, the combined use of an aqueous solution lacking organiccomplexing agent in the step 2 of the process (step b) of the process 1of the invention), with an increased amount of organic complexing agentin steps 1 and 3 (steps a) and d), respectively, of the process 1 of theinvention) (example 2, catalyst 2) leads to a synergistic effect on thecatalyst activity. An improvement of 107% on the catalyst activity isobtained.

It can also be observed that the polyol plays an important role in thecatalyst activity. If a polyol synthesized by acidic catalysis is used,its activity can be evenly more improved (138%).

In order to confirm the improved properties of a catalyst obtainedfollowing the process 1 of the invention, the results of comparativecatalyst 7 (obtained by a process which uses TBA in step 2) and catalyst2 of the invention, both having been obtained using a 50% higherproportion of TBA in steps 1 and 3, were also compared.

The results are shown in table II below:

TABLE II Activity of the catalyst 2 and comparative catalyst 7 measuredfollowing the process as described above. Activation Improvementpercentage time Catalyst activity with respect to comparative (min)(g/min) catalyst 4 Catalyst 2 21 31 107% Comparative 24 19.5 30%Catalyst 7

As can be seen, a markedly improvement in the catalyst activity of thecatalyst of the invention is obtained, which again demonstrates theunexpected effect conferred by the use of an aqueous solution lacking oforganic complexing agent for washing the catalyst in the second step(step b) of the process of the invention).

On the other hand, Table III shows the properties (unsaturation leveland polydispersity) of the polymers synthesized using catalysts 1-3 andcomparative catalysts 4-7.

TABLE III Polyol properties with different catalysts UnsaturationPolydispersity Catalyst 1 0.0071 1.17 Catalyst 2 0.0064 1.14 Catalyst 30.0069 1.15 Comparative Catalyst 4 0.0083 1.22 Comparative Catalyst 50.0091 1.25 Comparative Catalyst 6 0.0088 1.23 Comparative catalyst 70.0075 1.18

These data show that the catalysts of the invention provide polyetherpolyols having lower unsaturation levels and lower polydispersity thanthose obtained using other catalysts of the state of the art.

Example 9 Measurement of Catalyst Activity in the Synthesis of PolyolsUsing a Basic Initiator

The same polymerization reaction as described in example 8 was carriedout but replacing the acidic initiator by a basic initiator, i.e. a 700mol. wt. polyether polyol previously synthesized by basic catalysis.Catalyst 3 is used in the polymerization reaction.

Table IV shows the results on catalyst activity for catalyst 3 usingboth types of initiators (basic and acidic).

TABLE IV Catalyst activity using different initiators CatalystActivation activity Improvement Type of initiator time (min) (g/min)percentage Catalyst 3 700 mol. wt. polyether 9 35.7 28.4% polyol triolpreviously synthesized by acidic catalysis Catalyst 3 700 mol. wt.polyether 12 27.8 polyol triol previously synthesized by basic catalysis

As shown in Table IV, there is a further synergistic effect derived fromthe use of a polyol synthesized by acidic catalysis, as a ligand of thecatalyst and as an initiator of the polymerization reaction.

The invention claimed is:
 1. A process of preparing a double metalcyanide complex catalyst, said process comprising: a) synthesizing asolid double metal cyanide catalyst in the presence of an organiccomplexing agent and a polyether polyol ligand; and b) first washing thecatalyst obtained in step a) with an aqueous solution comprising:90-100% by weight of water; and 0-10% by weight of a polyether polyol,to form a slurry, wherein the aqueous solution does not contain anyorganic complexing agent.
 2. The process according to claim 1, whichfurther comprises: c) isolating the catalyst from the slurry obtained instep b); and d) washing the solid catalyst obtained in step c) with asolution comprising: 90-100% by weight of an organic complexing agent;and 0-10% by weight of a polyether polyol,  to form a slurry.
 3. Theprocess according to claim 1, wherein the synthesis of step a)comprises: producing a catalyst slurry by reacting an aqueous solutionof a metal salt with an aqueous solution of a metal cyanide salt in thepresence of an organic complexing agent; combining the catalyst slurrywith a polyether polyol ligand; and isolating a polyether-containingsolid catalyst from the slurry.
 4. The process according to claim 1,wherein the polyether polyol ligand is synthesized by acidic catalysis.5. The process according to claim 1, wherein the polyether polyol is adiol or a triol, having number average molecular weight lower than 2000.6. The process according to claim 1, wherein the organic complexingagent is selected from monoalcohols, aldehydes, ketones, ethers, esters,amides, ureas, nitriles, sulfides and mixtures thereof.
 7. The processaccording to claim 3, wherein the metal salt is selected from zincchloride, zinc bromide, zinc acetate, zinc acetonylacetate, zincbenzoate, zinc nitrate, iron (II) sulfate, iron (II) bromide, cobalt(II) chloride, cobalt (II) thiocyanate, nickel (II) formate, nickel (II)nitrate and mixtures thereof.
 8. The process according to claim 3,wherein the metal cyanide salt is selected from potassiumhexacyanocobaltate (III), potassium hexacyanoferrate (II), potassiumhexacyanoferrate (III) and calcium hexacyanocobaltate (III).
 9. Theprocess according to claim 1, wherein the synthesis of solid doublemetal cyanide catalyst is carried out at a temperature ranging from 30to 70° C.